It is well known that many utility installations, for example sewer pipes, waste water pipes, electric cable conduits, mains water supply control valves, transformers, and the like, are positioned below ground level. Access to these utility installations is generally achieved by climbing through an entrance hole at ground level and down a vertically extending access conduit, usually a cylindrical pipe having a diameter large enough to permit at least a person to gain access to the utility installation.
The access conduit entrance is invariably provided with a utility access cover which is usually fabricated from a rigid robust material such as cast iron or reinforced concrete and, as a result, is heavy and difficult to maneuver. Most usually, these utility access covers are fabricated from cast iron and have at least two holes near the outer circumferential edge of the cover for use in removing the cover from the entrance hole. In position, the cover is seated in a cover support ring situated such that the cover and the ring are substantially in the plane of the surrounding surface, such as that of the road or sidewalk surface. The technique usually employed for lifting and maneuvering these covers is to use a crow-bar, trap-hook, or similar metallic rod-like took by inserting the tool into one of the holes in the cover and pulling the tool outwards and upwards towards the operator, relying on the friction between the cover and the tool to effect lifting of the cover. Alternatively, the cover may be removed by forcing it out of its support ring by jamming a tool between the outer peripheral edge of the cover and the support ring. In both instances, very little control over the movement of the cover can be maintained and, furthermore, there is always the chance that the cover may drop off the tool and injure the operator.
In the U.S. patent application Ser. No. 080,233 (now U.S. Pat. No. 4,227,731), to Alfred B. Castle, the inventor of the tool of the present application, there is disclosed a lifting tool which can be used to conveniently lift and maneuver utility access covers, especially heavy cast iron manhole covers, while maintaining complete control over the movement of the cover and without risk of the cover becoming disengaged from the tool and possibly injuring the operator. The tool described in the above-mentioned application Ser. No. 080,233, the disclosure of which is specifically incorporated herein by reference, is particularly suited for lifting and maneuvering utility access covers provided with locking devices such as that described in U.S. Pat. No. 3,751,949 to Alfred B. Castle.
While the lifting tool described in the above-mentioned Ser. No. 080,233 works well for regular-sized circular manhole covers and small gratings, difficulties are still encountered in lifting and maneuvering larger manhole covers and gratings, in particular those employed, for example, to cover large below-ground-level transformer housings. A major problem with these larger covers and gratings is that, in view of their increased dimensions and weight (typically in the range 300 to 2000 pounds, e.g., 450 to 700 pounds), it is generally necessary to employ two or more persons for the cover handling operation, which increases labor costs significantly. In addition, while it may be possible for two or more persons to lift the cover from its retaining frame without the expenditure of too much effort, moving the covers away from the frame requires care and can be dangerous, as it is necessary to walk near the edges of the frame. Loss of control of the cover in the region of the frame could result in severe damage to the utility installation if the cover falls into the installation vault as well as severe physical injury to the persons involved.